LED flashlights have many advantages, including long life expectancy of the LED light source, and low current drain. However, with current LEDs, the beam size that they produce requires use of more than one LED when larger diameter flashlight beams are desired.
Cassegrain optics used in a two-mirror telescope can be traced to the mid 1600s. Though no successful telescopes were produced during this time, the idea was first conceived then and is now the most prominent type of large-scale telescope in production. The idea of the Cassegrain telescope is to fold incoming light using two mirrors and achieve long focal lengths with relatively little weight or size (as compared to the Newtonian-type telescope).
Light enters through the lens and is reflected off a spherical or parabolic primary mirror and is refracted onto a convex hyperbolic secondary mirror. In the specific application for use in a telescope, the focal length is adjusted to correctly display the image at the calculated position of the eyepiece which is typically slightly behind perforations in the primary mirror.
The present application proposes the use of Cassegrain optics in reverse, i.e., not to collect light and concentrate it, but to receive a narrow beam of high intensity light from an LED light source and expand its diameter to a larger size and lower intensity. This avoids the need for multiple LEDs to create a large diameter beam.